The present invention relates generally to improvements in camera and it relates particularly to an improved data recording device in a photographic camera.
Cameras heretofore available or proposed with a built-in data recording device may be classified into the following three types depending on the time when the data recording circuit operates.
(a) The data recording circuit which starts operating while the camera exposure control circuit is in operation.
(b) The data recording circuit which starts operating after the camera exposure control circuit has completed its operation.
(c) The data recording circuit which starts operating almost in synchronization with the commencement of the operation of the camera exposure control circuit.
With a camera of type (a), the data recording circuit is so arranged that it starts operating in response to the closure of the camera X contact. This arrangement may result in a high voltage being applied from an electronic flash to the data recording circuit, causing damage thereto. Additionally, when the electronic flash built into the camera body and the camera exposure control circuit operate on a common power supply, an overlap occurs between the time when the electronic flash unit is charged for subsequent firing after a flash in response to the closure of the X contact and the time when the data recording circuit operates. This overlap causes a power voltage variation, resulting in a malfunctioning of the data recording circuit.
With a camera of type (b), a power switch for the data recording circuit is maintained in its ON position when the camera shutter release button is depressed. As a result, releasing the shutter release button immediately after exposure may cause the power switch to be opened during the data recording period. Therefore, with this type of camera data recording system the desired data is not properly recorded under suitable exposure conditions.
A characteristic of the camera of type (c), is that the data recording circuit starts to operate immediately after the shutter release operation. However, there occurs an overlap between the operating times of the data recording circuit and the exposure control circuit. This results in a power voltage variation during the shutter exposure operation, causing the exposure control circuit to malfunction, whereby an exposure error occurs.
Specifically, the data recording circuits of the above type start operating simultaneously with, before or after the operation of the exposure control circuit in response to the shutter release operation, and completes its operation when the exposure circuit is in operation. The electrical loading by the data recording circuit of the power supply circuit is interrupted thereby causing the power voltage to over rebound, whereby the exposure control circuit is affected and fails to operate properly.